Stress that pushes a mass of rock in two opposite directions is called
a. shearing.
b. tension.
c. compression.
d. deformation.

The correct answer is A.

Stress that pushes a mass of rock in opposite directions is called shearing.

When shear stress occurs, the force of the stress pushes some of the crust in different directions. When this happens, a large  part of the crust can break off which makes the rock smaller. Shear stress happens more often at plate boundaries and usually occurs when passing plates rub against each other as they move in opposite directions.

The friction of shear stress at the edge of the plate can cause earthquakes.

The right answer is C. compression.